作 者 ：韩刚,赵忠*
期 刊 ：生态学报 2010年 30卷 15期 页码：4019~4026
Keywords:xerophilous shrub, light response of photosynthesis, drought stress,
摘 要 ：采用盆栽试验在适宜水分、中度干旱和重度干旱（土壤田间持水量的70%-75%、45%-50%和30%-35%）条件下，研究了4种沙生灌木柠条、花棒、沙木蓼和杨柴1年生幼苗的光合光响应特性。结果表明：各灌木光响应曲线的变化趋势基本一致，采用非直角双曲线模型拟合良好；各灌木净光合速率在同等光合有效辐射时均表现为适宜水分＞中度干旱＞重度干旱；各灌木在干旱条件下叶片表观量子效率与最大净光合速率均较适宜水分下降低，两项参数在中度与重度干旱下的平均降幅柠条均为最小，反映出柠条光合作用对干旱胁迫较强的适应性；干旱条件下光饱和点的降低是造成4种沙生灌木对光照需求改变的主要原因，光补偿点和饱和点的协同变化表明柠条具有对光环境良好的适应性；4种沙生灌木在干旱条件下暗呼吸速率均降低。在西北沙区人工植被建设中从光合特性考虑，柠条更宜作为土壤水分较差立地上的先锋树种。
Abstract:The soil drought was one of key factors limiting photosynthesis of trees in northwest desert areas of China. In order to clarify the patterns of response in photosynthesis of four local representative xerophilous shrubs Caragana korshinskii, Hedysarum Scoparium, Atraphaxis bracteata and Hedysarum mongolicum to soil drought, one-year-old seedlings of the four xerophilous shrubs were potted and grown under three soil water conditions: suitable soil moisture, medium drought and severe drought (corresponding soil water contents are respectively: 70%-75%, 45%-50% and 30%-35% of field moisture capacity). The light response curves and several parameters of photosynthesis were measured after the treatments. The results showed that the light response curves of the four xerophilous shrubs growing under different soil moisture had similar trend. Increasing the photosynthetic active radiation (PAR), the net photosynthetic rate (Pn) increased rapidly at first and then slowly. All of the coefficients of light response curve equations fitted using nonrectangular hyperbola model were above 0.95, meaning a compatibility between the model and the response process of photosynthesis of four xerophilous shrubs to light. For different xerophilous shrubs, changes of light response curves showed a similar regulation with reduced soil moisture, but Pn of four xerophilous shrub seedlings under suitable soil moisture＞ that under medium drought＞that under severe drought at same PAR, the differences was statistically significant with the PAR increasing. Compared with suitable soil moisture, the apparent quantum yield (AQY) and maximum net photosynthetic rate (Pnmax) of four xerophilous shrubs decreased under drought stresses. The average decreasing extent of the AQY in C. korshinskii under medium drought and severe drought was 10.16%, in H. Scoparium and H. mongolicum and A. bracteata was respectively 17.15% and 30.78% and 56.95%. The average decreasing extent of the Pnmax in C. korshinskii under medium drought and severe drought was 14.95%, in H. Scoparium and H. mongolicum and A. bracteata was respectively 41.97% and 53.09% and 5241%. That indicated C. korshinskii had an outstanding drought adaptation in photosynthesis. Under different soil moisture conditions, C. korshinskii and H. Scoparium were always typical sun plants. A. bracteata and H. mongolicum belonged to typical sun plants under suitable soil moisture and medium drought, but were between sun and shade plants under severe drought. The characters were certainly adapted to the natural conditions of drought and sufficient light source in the northwest desert areas of China. Under drought stresses, the decrease of light saturation point (LSP) was the main reason for changes in light requirement of four xerophilous shrubs. Especially under severe drought stress the LSP fell significantly, this could significantly decrease the capacity of four xerophilous shrubs to withstand strong light. According to the variations of light compensation point (LCP) and LSP, C. korshinskii not only maintained a steady use ability to high light but also increased the use of low light, showing considerably strong adaptability to light environment under drought stress. The dark respiration rates (Rd) of all of the four xerophilous shrubs decreased under drought stresses. This was conducive to reduce the influence of drought stress on dry matter accumulation of seedlings. From the results, C. korshinskii could be more suitable for artificial vegetation construction in desert areas of northwest China, and its planting in serious drought regions or during serious drought seasons should be avoided.
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